taxol

Taxol is the trade name for the chemical paclitaxel and is well known for its use in chemotherapy.

In 1958 the US National Cancer Institute began to screen 35,000 plant species for anticancer activity. Five years later anticancer activity was discovered in extracts from the bark of the Pacific yew tree (Taxus brevifolia) ; by 1971 paclitaxel was shown to be the active ingredient.

The discovery in 1979 that paclitaxel interferes with cell division (mitosis) made it the primary candidate for a new type of anti cancer drug. Clinical trials proved that it had great potential as a treatment for ovarian cancer and lot of work was carried out by Bristol-Myers Squibb Company to develop it further, and it was registered as Taxol.

The Pacific yew is extremely slow growing and a protected species - the extraction of enough chemical to treat one patient would mean the death of six 100 year old trees.
Fortunately a very similar molecule, baccatin II, which could be converted into semisynthetic taxol, was isolated from a renewable source, the European yew, (Taxus baccata), and clinical trials were very impressive. It received clearance from the FDA in 1995. Sadly the chemical conversion is very time consuming and expensive - a major drawback to the use of semisynthetic Taxol because it makes it a very expensive drug to manufacture.

Work is continuing to make a totally synthetic version of taxol, and also to create molecular modifications which might improve its efficacy. Along another line of research, biotechnologists are attempting to extract the drug from cultivated Pacific yew cells growing in vats in order to speed up production. Other varieties of yew are also under investigation as potential sources of this valuable drug.